Deuterated Semiconducting Organic Compounds for Use in Light-Emitting Devices

ABSTRACT

The present invention discloses deuterated semiconducting organic compounds. The deuterated semiconducting organic compounds comprise at least one partially or fully deuterated non-conjugated portion linked to the conjugated portion. The mentioned deuterated semiconducting organic compounds can be used in optoelectronic devices, such as light-emitting devices and photodiodes, with enhanced performance and lifetime. The deuterated semiconducting organic compounds of this application can be employed as emissive layer, charge-transporting layer, or energy transfer material in organic light-emitting devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to semiconducting organiccompounds for use in optoelectronic devices, and more particularly todeuterated semiconducting organic compounds for use in light-emittingdevices.

2. Description of the Prior Art

Organic light emitting diodes (OLEDs) are under intensive investigationbecause of their potential of achieving improved device performances.OLED has the advantages of self-light, wide view angles, beinglightweight, fast response time, and low power consumption, etc.Although having many advantages, organic light-emitting materials stillsuffer from some drawbacks, such as low light emission efficiency andpoor high-voltage stability. In view of the above matter, developing anovel organic compound having high voltage stability and low turn-onvoltage to prolong the usage lifetime of the device and to increaseluminance efficiency is still an important task for the industry.

SUMMARY OF THE INVENTION

According to the above, the present invention provides new deuteratedsemiconducting organic compounds for using in light-emitting devices tofulfill the requirements of this industry.

One object of the present invention is to employ deuteratedsemiconducting organic compounds for using in light-emitting devices. Bypartially or fully deuterated the protons of the semiconducting organiccompounds, the high voltage stability of the light-emitting devices canbe increased, and the turn-on voltage can be decreased. Thus, the usagelifetime of the light-emitting devices can be prolonged efficiently.

Another object of the present invention is to employ deuteratedsemiconducting organic compounds for using in light-emitting devices. Bypartially or fully deuterated the protons of the semiconducting organiccompounds, the external quantum efficiency and the light emissionefficiency of the light-emitting materials can be increased, and thus,the luminance efficiency of the light-emitting devices can be improved.

According to above-mentioned objectives, the present invention disclosesdeuterated semiconducting organic compounds for using in light-emittingdevices. The deuterated semiconducting organic compounds comprise atleast one conjugated portion, and at least one non-conjugated portionlinked to the conjugated portion. The protons linked to thenon-conjugated portion are partially or fully deuterated. Thelight-emitting device comprises a pair of electrodes and one or moreorganic layers disposed between the electrodes. The mentioned deuteratedsemiconducting organic compounds are employed in the organic layers.Mostly, the deuterated semiconducting organic compounds are used as hostmaterials or guest materials in the light-emitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a˜1 c show external quantum efficiency as a function of currentdensity in a device of ITO/(H- or D-)Q₂AlOAr (50 nm)/Alq₃ (30 nm)/Mg:Ag(10:1), wherein the voltage was applied from 0 to 18 V and back to 0 Vfor consecutively two cycles for each device, and the EL maximum islocated at 490 nm for the protonated device and at 500 nm for thedeuterated device as designated in the figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

What is probed into the invention is organometallic complexes and theirapplication. Detail descriptions of the structure and elements will beprovided in the following in order to make the invention thoroughlyunderstood. Obviously, the application of the invention is not confinedto specific details familiar to those who are skilled in the art. On theother hand, the common structures and elements that are known toeveryone are not described in details to avoid unnecessary limits of theinvention. Some preferred embodiments of the present invention will nowbe described in greater detail in the following. However, it should berecognized that the present invention can be practiced in a wide rangeof other embodiments besides those explicitly described, that is, thisinvention can also be applied extensively to other embodiments, and thescope of the present invention is expressly not limited except asspecified in the accompanying claims.

One preferred embodiment of this present invention discloses smallmolecular deuterated semiconducting organic compounds, wherein thedeuterated semiconducting organic compounds is not polymers. Thedeuterated semiconducting organic compounds comprise at least oneconjugated portion, and at least one non-conjugated portion linked tothe conjugated portion. The protons of the non-conjugated portion arefully or partially deuterated. In some examples, the protons of theconjugated portion are also deuterated.

The non-conjugated portion of the deuterated semiconducting organiccompounds is selected from the group consisted of C₁˜C₃₀ linear alkyl,C₁˜C₃₀ branch alkyl, C₁˜C₃₀ cyclic alkyl, C₁˜C₃₀ alkoxyl, C₁˜C₃₀ silyl.In one preferred example of this embodiment, the semiconducting organiccompound further comprises a metal, wherein said metal is selected fromLi, Na, K, Be, Mg, Ca, Ti, Cr, Mo, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd,Pt, Cu, Zn, Cd, B, Al, Ga, In, Si, N and P.

The deuterated semiconducting organic compounds can be used inoptoelectronic devices, such as light-emitting devices, and photodiodes,with enhanced performance and lifetime. In one example of thisembodiment, the deuterated semiconducting organic compounds can beemployed as emissive layer, charge-transporting layer, or energytransfer material in organic light-emitting devices, wherein theconjugated portion of the deuterated semiconducting organic compounds isused as chromophore.

Another preferred embodiment of the present invention disclosesdeuterated semiconducting organic compounds for using in optoelectronicdevices. The general structure of the deuterated semiconducting organiccompounds comprises at least one conjugated portion and at least onenon-conjugated portion. The protons of the non-conjugated portion arepartially or fully deuterated. The non-conjugated portion of thedeuterated semiconducting organic compounds is selected from C₁˜C₃₀linear alkyl, C₁˜C₃₀ branch alkyl, C₁˜C₃₀ cyclic alkyl, C₁˜C₃₀ alkoxyl,C₁˜C₃₀ silyl.

In one preferred example of this embodiment, the protons of theconjugated portion are also partially or fully deuterated. In anotherpreferred example of this embodiment, the deuterated semiconductingorganic compounds comprise at least one metal. The metal is selectedfrom Li, Na, K, Be, Mg, Ca, Ti, Cr, Mo, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni,Pd, Pt, Cu, Zn, Cd, B, Al, Ga, In, Si, N and P.

The mentioned deuterated semiconducting organic compounds can be appliedin organic electroluminescence devices, organic phosphorescence devices,solar cells or other organic optoelectronic devices.

In one preferred example of this embodiment, the deuteratedsemiconducting organic compounds are used in light-emitting devices. Theabove light-emitting device comprises a pair of electrodes, and one ormore organic layers disposed between the electrodes. The organic layerscomprise a light-emitting layer, and at least one of the organic layerscomprises the deuterated semiconducting organic compounds. Thedeuterated semiconducting organic compounds comprise at least oneconjugated portion as the chromophore of the light-emitting device, andat least one non-conjugated portion linked to the conjugated portion.The protons of the non-conjugated portion are partially or fullydeuterated. In some examples, the protons of the conjugated portion arepartially or fully deuterated. Furthermore, the deuteratedsemiconducting organic compounds can further comprise at least one metalselected from Li, Na, K, Be, Mg, Ca, Ti, Cr, Mo, Mn, Fe, Ru, Os, Co, Rh,Ir, Ni, Pd, Pt, Cu, Zn, Cd, B, Al, Ga, In, Si, N and P. According tothis example, the deuterated semiconducting organic compounds can beemployed as the host materials, or the guest materials in thelight-emitting device. In one example of this embodiment, the mentioneddeuterated semiconducting organic compounds can be used inlight-emitting device such as organic light-emitting diode (OLED) orpolymer light-emitting diode (PLED).

The preferred examples of the structure and fabricating method for thedeuterated semiconducting organic compounds according to the applicationare described in the following. However, the scope of this applicationshould be based on the claims, but is not restricted by the followingexamples.

General Deuteration Procedure:

The deuteration of 8-hydroxyquinoline, 2-methyl-8-hydroxyquinoline, and2,6-dimethylphenol was achieved by the following procedures. [Keyes, T.E.; O'Connor, C. M.; O'Dwyer, U.; Coates, C. G.; Callaghan, P.;McGarvey, J. J.; Vos, J. G. J. Phys. Chem. A 1999, 103, 8915; and Keyes,T. E.; Weldon, F.; Muller, E.; Pechy, P.; Gratzel, M.; Vos, J. G. J.Chem. Soc., Dalton Trans. 1995, 16, 2075]Briefly, 500 mg of8-hydroxyquinoline (or other compounds) was dissolved/dispersed in amixed solution containing 30 mL of D₂O, 5 mL of acetone-d6, and 0.5 g ofa catalyst Pd/C (10% Pd, Aldrich) in a Teflon-coated stainless steelhigh-pressure reactor, which was then heated in an oven at 220° C. for48-72 h. After reaction, the stainless steel reactor was allowed to coolto room temperature. The solid catalyst was filtered off and washed bydichloromethane and acetone for a few times. The product was collectedby vacuum removal of the solvents. The percentage of deuteration wasdetermined by FTIR spectroscopy, mass spectrometry, and 1H NMRspectroscopy.

In some examples according to this application, the above products arefurther used to synthesize metal complex by the following procedures.[Tang, C. W.; VanSlyke, S. A. Appl. Phys. Lett. 1987, 51, 913; andCurioni, A.; Boero, M.; Andreoni, W. Chem. Phys. Lett. 1998, 294, 263]The deuterated compounds were purified by a train-sublimation process inan oven under a temperature gradient and a pressure of 10⁻³ Torr andrecrystallized in ethanol. Compounds were identified by NMRspectroscopy, mass spectrometry, and X-ray crystallography.

Procedures for Measurements of Fluorescence Lifetime and Quantum Yields:

Luminescence quantum yields (Φ_(F)) of H-Alq₃ and D-Alq₃ were determinedusing fluorescein (Φ_(F)) 0.90, in 0.1 M NaOH) as a standard under adegas condition. Fluorescein has two absorption maxima at 320 and 496nm. The absorbances of fluorescein and Alq₃ in N,N-dimethylformamide(DMF) at 320 nm were adjusted to be the same when measuring thefluorescence quantum yield. The quantum yields, measured under a degascondition in DMF, were 0.11 and 0.19 for H-Alq₃ and D-Alq₃,respectively. H-Alq₃ and D-Alq₃ show the same UV-visible absorption andphotoluminescence (PL) spectra. Fluorescence lifetime measurements werecarried out in a single-photon counter (Edinburgh, model OB900,England). The fluorescence quantum yields of H- and D-Q₂AlOAr weremeasured in a similar way.

OLED Device Fabrication:

The ITO glass (Merck) with 80 nm thickness of ITO was ultrasonicallycleaned in an aqueous solution, followed by a patterning process.Electroluminescence materials were then deposited onto the patterned ITOglass in a thermal evaporator at a pressure of 5×10⁻⁶ Torr. The cathodeconsisted of Mg:Ag (10:1, total 55 nm) by coevaporation of Mg and Agmetals at a deposition rate of 5-7 and 0.5-0.7 Å s⁻¹, respectively. Thecurrent-voltage-luminescence (I-V-L) measurements were carriedsimultaneously using a Keithly 2400 Source meter and a Newport 1835-Coptical meter with a Newport 818-ST silicon photodiode as the detector.The electroluminescence (EL) spectra of as-fabricated devices weremeasured on a Hitachi F-4500 luminescence spectrometer. The deuteratedand protonated devices for the light emitter were fabricated in the samebatch at the same day to avoid any contribution from variation in thefabrication process. The fabrication of devices was repeated at leastthree times to warrantee the reproducibility of the reported phenomena.

In one preferred example of this application, H-Q₂AlOAr and D-Q₂AlOArare used as the semiconducting organic compounds and following thementioned process to fabricate the light emitting devices. TheElectroluminescence properties of the devices are shown as FIG. 1 a˜1 c.

As shown in FIG. 1 a and FIG. 1 b, the EL intensities and currentdensities increase almost linearly at higher applied voltages. The ELintensities, however, drop quickly upon the applied voltage passing acritical value of ˜15.2 V for D-Q₂AlOAr and 15.8 V for H-Q₂AlOAr,respectively. The external quantum efficiency of the D-Q₂AlOAr device ishigher than that of the H-Q₂AlOAr device at all current densities,1.9-fold at 50 mA/cm² and ˜2.8-fold at 150 mA/cm². After experiencingthe high-voltage-induced degradation in the first cycle, the externalquantum efficiency of the D-Q₂AlOAr device becomes 3.5-fold of theH-Q₂AlOAr device at 150 mA/cm². And the D-Q₂AlOAr device loses 35%external quantum efficiency in the second forward (low-to-high) halfcycle at 150 mA/cm², which is smaller than the 49% loss in the H-Q₂AlOArdevice. The slightly lower critical high voltage of 15.2 V for D-Q₂AlOAris due to a higher current density of the deuterated device itself. Inthe above green and blue EL devices, it was also noticed that thedeuterated devices have lower turn-on voltages in both green (by ˜0.8 V)and blue (by ˜2.5 V) devices. The cause for lower turn-on voltages indeuterated devices could be a result of higher light-emittingefficiencies of the deuterated light-emitting materials.

To sum up, the present application discloses deuterated semiconductingorganic compounds for using in optoelectronic devices, especially inlight-emitting devices. The light-emitting device comprises a pair ofelectrodes, and one or more organic layers disposed between theelectrodes. At least one of the organic layers comprises the deuteratedsemiconducting organic compounds. By partially or fully modifying theprotons of the semiconducting organic compounds with deuterium, the highvoltage stability of the light-emitting devices can be increased, andthe turn-on voltage can be decreased. Therefore, the usage lifetime ofthe light-emitting devices can be prolonged efficiently. Furthermore, byemploying the deuterated semiconducting organic compounds If thisapplication, the external quantum efficiency and the light emissionefficiency of the light-emitting materials can be increased, and theluminance efficiency of the light-emitting devices can be efficientlyimproved.

Obviously many modifications and variations are possible in light of theabove teachings. It is therefore to be understood that within the scopeof the appended claims the present invention can be practiced otherwisethan as specifically described herein. Although specific embodimentshave been illustrated and described herein, it is obvious to thoseskilled in the art that many modifications of the present invention maybe made without departing from what is intended to be limited solely bythe appended claims.

1. A light-emitting device comprising: a pair of electrodes and one or more organic layers disposed between said electrodes, said one or more organic layers comprising a light-emitting layer, wherein at least one of said one or more organic layer comprises a semiconducting organic compound with a conjugated portion and at least one non-conjugated portion linked to the conjugated portion, wherein protons of said non-conjugated portion are partially or fully deuterated.
 2. The light-emitting device according to claim 1, wherein said non-conjugated portion is selected from the group consisted of C₁˜C₃₀ linear alkyl, C₁˜C₃₀ branch alkyl, C₁˜C₃₀ cyclic alkyl, C₁˜C₃₀ alkoxyl, C₁˜C₃₀ silyl.
 3. The light-emitting device according to claim 1, wherein the protons of the conjugated portion are partially or fully deuterated.
 4. The light-emitting device according to claim 1, wherein the semiconducting organic compound further comprises a metal, wherein said metal is selected from Li, Na, K, Be, Mg, Ca, Ti, Cr, Mo, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Zn, Cd, B, Al, Ga, In, Si, N and P.
 5. The light-emitting device according to claim 1, wherein the semiconducting organic compound is used as the host material in the light-emitting device.
 6. A small molecular deuterated semiconducting organic compound for using in an optoelectronic device, comprising: at least one conjugated portion, wherein the protons of the conjugated portion are partially or fully deuterated; and at least one non-conjugated portion linked to said conjugated portion, wherein the protons of the non-conjugated portion are partially or fully deuterated.
 7. The small molecular deuterated semiconducting organic compound according to claim 6, wherein said non-conjugated portion is selected from the group consisted of C₁˜C₃₀ linear alkyl, C₁˜C₃₀ branch alkyl, C₁˜C₃₀ cyclic alkyl, C₁˜C₃₀ alkoxyl, C₁˜C₃₀ silyl.
 8. The small molecular deuterated semiconducting organic compound according to claim 6, further comprises a metal, wherein said metal is selected from Li, Na, K, Be, Mg, Ca, Ti, Cr, Mo, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Zn, Cd, B, Al, Ga, In, Si, N and P.
 9. The small molecular deuterated semiconducting organic compound according to claim 6, wherein the conjugated portion is used as chromophore in a light emitting device. 